1. Field of the Invention
The present invention relates to a direct or indirect method for adjusting the predefined calibration on reagents suitable for performing diagnostic tests in the field of medical biology and more specifically that of haemostasis.
2. Description of the Related Art
Haemostasis is considered to be a set of physiological mechanisms involved in preventing and stopping bleeding.
Haemostasis is frequently compared to scales, as blood fluidity is maintained by means of a balance between clotting factor activators and inhibitors.
Any disruption in this balance will tip the scales towards a pathological process: thrombosis, resulting from the formation of a clot liable to be caused by inhibitor deficiency, or haemorrhaging resulting from bleeding liable to be caused by clotting factor deficiency.
Analysing and assaying clotting activating or inhibiting factors thus makes it possible to diagnose predisposition or risks of thrombosis or haemorrhaging in various clinical situations.
These tests are mainly performed routinely in testing laboratories or hospitals, in a semi-automated or automated manner.
Generally, depending on the tests performed and instruments used, the results consist either of a signal measured by the instrument or of a biological activity calculated by the instrument.
As for most biological tests performed on test systems, when performing an automated haemostasis test, a calibration is required to calculate the level or activity of the factor under study directly. These calibration data are generally obtained using calibrators with a well characterised activity or concentration of the target test substance and on the basis of which calibration curves can be defined to assign a concentration or activity to a given signal intensity.
However, insofar as the same test may frequently be performed on systems from different ranges, it is frequent to observe between-instrument variability. This variability does not always enable direct comparison, for the same test, of the results obtained on different apparatuses always using the same standard calibration.
Moreover, since a large number of reagents are in liquid form, they may be more susceptible to the ageing phenomenon than reagents in freeze-dried form. For this reason, even though these reagents remain functional for a certain time, the sensitivity thereof may nevertheless decrease partially or vary over time.
This results in a difficulty interpreting the results obtained using the same reagent but arising from tests performed over different periods.
The application US 2007/0020765 describes a method for standardising the clotting time of a sample, wherein at least two calibrators are used, for which standard clotting times have been predetermined in the same test system as that applied to the sample, and on the basis whereof a calibration curve is defined between the predetermined standard times and the actual times measured for the same calibrators, in the test used.
The clotting time measured in the sample is converted into a standardised clotting time using the calibration curve defined.
Therefore, this method consists of creating a calibration locally whenever a new kit is used to measure a clotting time in a haemostasis test.